X-ray tube and vacuum control therefor.



H. O. SNOOK & G. H. WHITE. X-RAY TUBE AND VACUUM CONTROL THEREFOR.

APPLICATION FILED APR.7, 1911. v

Patented Nov. 28, 1911.

MJVENTORS a {AM/9 BY Z1? ATTORNEY UNITED STATES PATEN OFFICE.

HOMER CLYDE SNOOK AND GEORGE HERBERT WHITE, O'F PHILADELPHIA, PENNSYL- VANIA, ASSIG-NORS T0 ROENTGEN MANUFACTURING COMPANY, OF PHILADELPHIA, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA.

X-RAY TUBE AND VACUUM CONTROL THEREFOR.

To all whom it may concern:

Be it known that we, HOMER CLYDE SNooK and GEORGE HERBERT \VHITE, citizens of the United States, residing at Philadelphia, in

the county of Philadelphia and State of:

lar stems 1 and 2, and the vacuum regu- Pennsylvania, have invented new and useful Improvements in X-Ray Tubes and Vacuum Control Therefor, of which the following is a specification.

Our invention relates to X-ray tubes and more particularly to the structure of X-ray tubes and their mode of use.

Our invention relates to improvements in the structure of an X-ray tube, particularly as to the vacuum regulator therefor, which has an external terminal located with respect to the external cathode or negative terminal of the X-ray tube as hereinafter described.

Our invention resides also in apparatus for controlling the vacuum of an X-ray tube, whereby the vacuum within the tube is adjusted only at the will of the operator when, by the appearance of the glow of the tube, he desires to change the vacuum. This is accomplished, not automatically and not by a shunt circuit or path, as customary heretofore and as described, for example, in prior patent to Sayen No. 594,036, but is accomplished by switching mechanism whlch is operated only at the willof the operator and not in automatic response to any condition of vacuum in the X-ray tube. The switching mechanism when operated actually transfers one of the supply circuit terminals from one of the terminals of the X- ray tube to the vacuum regulator terminal,

' so that while the vacuum is being adjusted lator.

Our invention resides in the matters hereinafter described and claimed.

For an illustration of one of. the forms our invention may take, reference is to be had to the accompanying drawlng, in which:

Figure 1 is a side elevational view of our improved X-ray tube, together with a diagram of circuits illustrating its mode of use or operation. Fig. 2 is a sectional view on Specification of Letters Patent. Patented N 28" 1911;

Application filed April 7, 1911.

Serial No. 619,462.

the line 2 -2, of Fig. 1. Fig. 3 is a cross sectional view on the line 3-3, Fig, 1,

through the target or anode.

The X-ray tube comprises the usual glass bulbous portion X, the integral glass tubulator 3.

At 4 is indicated the glass tip at which the exhausting or pumping is performed and which is sealed off when the proper degree of vacuum within the X-ray tube is procured.

The target or anode proper is a block or sheet of platinum or other suitable refractory material 5,-secured upon the plug 6 fittlng in a hole or bore in the mass 7 of copper or other suitable material. The plug 6 is inserted to such distance that the outer surface of the plate 5 is somewhat below the surface 8 of the member 7 The member 7 has a neck 9 fitting snugly into and secured to the copper or other tubular member 10 fitting within the stem 1. This neck 9 may be bored out, as indicated in dotted lines, to make the parts lighter in weight, if desired.

The tubular member 10 is longitudinally slotted at 11 and has a plurality of transverse slots 12 intersecting the longitudinal slot- 11. This provides a plurality of independently yielding and resilient members WhlCh frictionally engage the inside of the glass neck 1. And the tubular member 10 itself frictionally engages the inside of the neck 1. The slotting as described, insures that the tubular member 10 shall engage the interior surface of the neck 1 at a plurality of points or over a relatively extended area, so as to frictionally hold the tube 10 and attached parts in the position shown, and prevent the tube 10 and attached parts from moving under the effects of shocks and other effects, to which the tube may be subjected in shipment or in usage.

By this construction the pressure per unit area on the interior of the glass stem is not made so great, by our method, to effect the same total friction. That is, the strain per unit area in the glass is made low 'by our method, so that the danger of breakage is reduced. By our construction we secure greater friction and immovability of parts, with less concentrated strain, than by former methods using similar materials. Our construction prevents not only longitudinal movement of the tube 10 and attached parts, but also rotative movement thereof.

Electrically connected to the tube 10, and therefore to the target 5, is the copper or other conductor 13 hard soldered to the lip 14 integral with the tube 10. Electrically joining the conductor 13 to the terminal 15 is the platinum or similar wire 16 sealed through the end of the neck 1.

As above stated, the target 5 has its surface slightly below the surface 8 of the memher 7. The edges of the opening around the target 5 operate as a diaphragm to sharply define the rays emanating from the target 5.

The cathode 17 has the usual concave surface 18 and is preferably turned out of a solid block of metal. Into the smaller bore 19 of the cathode 17 extends the conducting rod 20 inclosed in the inner glass stem or tube 21 which extends into the larger bore 22 of the cathode 17. A'platinum or other conductor 23 electrically connects the rod 20 and therefore the cathode 17 with the outer terminal 24, the platinum wire being sealed. within glass in the manner well understood.

We have found that where the external surface of the cathode 17 is parallel or substantially so, even for relatively slight dis tances, with the inner walls of the X-ray tube X or the neck 2, there is a bombardment from that surface against the glass of the tube, tending to rupture or weaken the X-ray tube. We have foundthat this may be prevented by sloping the exterior surface of the cathode from its front edge 25 backwardly and to smaller and smaller diameters, as indicated in the drawing. From the edge 25 the contour of the cathode 17 is curved backwardly and to smaller diameters as indicated, though it is to be understood that our invention is not limited to the precise curve here shown.

In the regulating neok3 is disposed a mass 26 ofasbestos or other material which will liberate gas to reduce the vacuum in the X: ray tube X. With this material communicates a conductor sealed through the glass and connecting to the terminal 27.

During the use of the X-ray tube the vacuum becomes rarer and rarer until finally so small a current passes through the tube that insuflicient X-rays are generated. To reduce the vacuum, the passage of current through gas liberating material in communication with the interior of the tube is resorted to and the conventional direction of electric current through this material should be from the interior of the tube through this material to the exterior terminal of this material. This regulation has been. heretofore accomplished by an automatically acting shunt'path having an adjustable finger or conductor extending partway between the negative or cathode terminal of the tube and an exterior terminal of the vacuum regulator. Then, as the vacuum in the tube became rarer and the resistance to passage of current through the tube increased, the potential difference applied to the terminals of'the tube would be suflicient to jump this external shunt gap between the negative terminal of the tube and the terminal of the vacuum regulator, causing passage of energy across the shunt gap to the cathode or negative terminal of the tube resulting in liberating gas to reduce the vacuum, whereupon the current would then again pass in sufiicient quantity within the tube to generate suflicient quantity of X- rays, and the sparking in the external gap would cease. By our arrangement we entirely dispense with this automatic regulator, and, indeed, locate the external terminal 27 of the gas producing material, as 26,

at so great a distance from the negative or cathode terminal 24,-that a regulating spark will not jump between terminals 27 and 24: no matter what the degree of vacuum within the tube X. Indeed, the distance between these terminals 27 and 24 in our construction is so great that the sparking potential between them is in excess of the potential to which the tube X may safely be subjected. That is, before a spark would leap the tube would be broken by the electrical pressure exerted upon it. For this reason, we have located the regulator preferably beyond the vertical central axis of the tube X, to the left of the same, and much nearer to the positive terminal 15. There is a symmetry of resistance within the X-ray tube which makes it easier for energy to pass from the anode within the tube out through the gas liberating material to the exterior terminal thereof than from the positive terminal through air to the terminal 27 and thence through the gas liberating material 26 within the tube .to the cathode 17. Therefore, we have found that the terminal 27 may be located quite near to the positive terminal 15 without danger of sparking between these points, and if sparking did occur,'it would have practically no effect upon changing the vacuum within the tube X; and atthe same time, the terminal 27 is located at such a great distance from the negative terminal 24, as above stated, that no sparking will ever occur.

To supply energy to our tube we may employ, by way of example, the following apparatus: G is a source of alternating current having its terminals connected to the contacts 28 and 29 of a reversing switch R. The consumption circuit terminals 30 and 31 of the reversing switch connect with the primary P of a transformer T, such as described in prior Letters Patent of the United .tact 3 States No. 954,056. S .is the high potential secondary winding of said transformer,

whose one terminal connects with the conducting arcs 7 and 9, and whose other terminal connects with the conducting arcs 3 and 5 of a rectifying switch such as descrlbed in the aforementioned Letters Patent. Opposed to the arcs 3, 5, 7 and 9 are the conducting arcs 4, 6, 8 and 10, of which arcs 4 and 10 are electrically connected together and of which arcs 6 and 8 are electr cally connected together. Cooperating w1th these opposed pairs of conducting arcs are the rotating cross connectors 1", t, u and 11, carried by the rotating shaft m adapted to be driven in synchr'onism or mechanically connected to the rotating element of the alternating current generator Gr. By the use of this apparatus uni-directional high potential current is delivered to the terminals 32 and 33. With the terminal 32 connects a movable conducting arm 34 and with the terminal 33 connects a similar arm 35. The terminal 32 is normally positive with respect to the terminal 33, and normally the movable conducting arm 34 is in contact with terminal 36 and the movable conducting arm 35 is in engagement with contact 37, contact 36 being connected by conductor 7 38 with the positive terminal 15 of the X- ray tube, and the contact 37 connected by conductor 39 withthe negative terminal 24 of the X-ray, tube. A third terminal 40 is provided and the same connects by conducwith the external terminal 27 of the tor 41 gas liberating material 26.

With the parts in the position shownin the drawing, the tube will be traversed by energy from the high potential rectifying switch,,such energy entering by terminal 15 and leaving by terminal 24. If the vacuum within the tube ,becomes too rare, it is reduced by the operator who moves the arm 35 from the position shown in full lines in Fig. 1, to'the position shown in dotted lines, thereby bringing the terminal 33 into electrical communication with terminal 40, by

actual manual transposition of switch arm 35, which then makes the terminal 27v the negative terminal of the tube, terminal 24 Current will now pass in series through the "terminal 15 and from the anode within the tube through the gas liberating material 26, thence to the terminal 27, thence to contact 40, thence to contact 33, the negative terminal of the rectifying switch. This flow of energy is in proper direction to liberate gas and will liberate enough gas to reduce the vacuum. Then the member 35 may be swun back a ain into engagement with conand -rays again generated, the desired degree of .vacuum being determined by the experience of the operator, who can determine from said external terminal for said the nature of the discharge within the tube when the vacuum is suitable to his purposes. If, however, the vacuum has become so rare and the resistance of the X-ray tube so high that, when the arm 35 is in engagement with contact 40, a spark will sooner pass between terminals 15 and 27, the operator returns the arm 35 to engagement with contact 37 and the arm 34 is moved to dotted line position into engagement with cont-act 40 and then the reversing switch R is thrown to its other position, whereupon 33 becomes the positive terminal of the rectifying switch and 32 the negative terminal. In such case, current will then pass into the tube in series through the terminal 24 and member 17, thence through the material 26 and out to the terminal 27, toterminal 40, and thence to the then negative terminal 32. This operation will then efi'ectually reduce the vacuum. From the foregoing description, it is, therefore, apparent that the X-ray tube cannot even accidentally automatically regulate by any sparking in the air between any of the terminals 15, 24 or'27.

While we have described the apparatus of the aforementioned Letters Patent as the means for producing the high potential unidirectional current, it is to be understood that any other suitable apparatus may be employed for this purpose, contacts 32 and 33. being in such cases again the positive and negative terminals of the high potential uni-directional source.

While the terminals 32 and 33 are shown in the diagram as closer together than the terminals 15 and 24, it is to be understood that this is illustrative only and that they are to be so separated that sparking will not occur between them. The same applies to the distances between the terminals 36, 40 and 37.

It is, of course, understood that the conducting arms 34 and 35 should not simultaneously be brought to terminal 40, for in that case the source of energy would be short circuited.

What we claim is:

' 1. An X-ray tube comprising a bulb and electrode stems integral therewith, a hollow neck attached directly to and communicating with theinterior of said bulb, gas lib erating material in said neck. an external terminal for said gas liberating materlal,

gas liberating material and the external negative terminal of' said X-ray tube separated by a gap preventlng sparking between said external terminals for any degree of vacuum of said X-ray tube.

2. An X-ray tube comprising a bulb and electrode stems integral therewith, a hollow neck attached directly to and communicating with the interior of said bulb, gas liberating material in said. neck, an external terminal for said gas liberating material, said external terminal of said gas liberating material separated from the external negative terminal of said X-ray tube by agap whose disruptive voltage is greater than the voltage which said X-ray tube can withstand.

3. An X-ray-tube comprising a bulb and electrode stems integral therewith, a neck attached directly to and communicating with the interior of said bulb, gas liberating material in said neck, an external terminal for said gas liberating material, an anode having its surface inclined to the axis of the anode stem, said neck containing gas liberating material, attached to said bulb in a region behind said anode surface, said external terminal for said gas liberating material separated from the external negative terminal of said X-ray tube by a gap whose disruptive voltage is greater than the voltageimpressed upon said X-ray tube.

4. The combination with an X-ray tube having external. positive and negative terminals, of a vacuum regulator, an exterior terminal therefor, a source of energy, a switch, one terminal of said switch connected with said negativeterminal and another terminal of said switch connected with said vacuum regulator terminal, and a terminal of said switch connected with the negative terminal of said source of energy, whereby the negative terminal of said source of energy may be isolated from said negative terminal of said X-ray tube and brought into electrical communication with said vacuum regulator terminal, said external vacuum regulator terminal separated from said external negative terminal of said X-ray tube by a gap whose disruptive voltage is greater than the voltage impressed by said source of energy upon the positive and negative terminals of said X-ray tube.

5. The combination with an X-ray tube having external positive and negative terminals, of a vacuum regulator, an exterior terminal therefor, a source of energy, a switch, one terminal of said switch connected with the positive terminal of said source of energy, another terminal of said switch connected with the positive terminal of said X-ray tube, and another-terminal of said switch connected with said vacuum regulator terminal, whereby said positive terminal of said source of energy may be isolated from said positive terminal of said X-ray tube and brought into electrical communication with said vacuum regulator terminal, said external vacuum regulator terminal separated from said externalnegative terminal of said X-ray tube by a gap whose tive terminal of said source of energy may be isolated from saidnegativeterminal of said X-ray tube and brought into electrical communication with said vacuum regulator terminal,

7. The combination with an X-rayv tube having external positive and negative terminals, of a vacuum regulator, an exterior terminal therefor, a, source of energy, a switch, one terminal of said switch connected with the positive terminal of said source of energy, another terminal of said switch connected with the positive terminal of said X-ray' tube, ,and anotherterminal of said switch connected with said vacuum regulator terminal, whereby said positive terminal of said source of energy may be isolated from said positive terminal of said 'X-ray tube and brought into electrical'communication with said vacuum regulator terminal.

8. The combination with an X-ray tube having external positive and negative terminals, of a vacuum regulator, an exterior terminal therefor, a source of ener ,and switch mechanism for transferring eit er of the ter: minalsof said sourc of energy from their normally'cooperatiiigtube terminals to said vacuum regulator terminal, said external vacuum regulator terminal separated from said external negative terminal of said X-ray tube by a gap whose disruptive voltage is greater than the voltage impressed by said source of energy upon the tive terminals of said X-ray tube.

In testimony whereof we have hereunto afiixed our signatures this 6th day of April, 1911, in the presence of the two subscribing witnesses:

Witnesses:

ELEANOR T. MoC'ALL, ANNA STEINBOCK.

positive and nega- Correction in Letters Patent N0.1,010, 197.

It is hereby certified that 1n hebbul'u In ent no. 1,010,197 granted November 28,

l 1911, upon the application of Homer Clyde Snook and George- Herbert White, of

Philadelphia, Pennsylvania, for an improvement inf X-Ray Tubes and Vacuum Control Therefor, an error appears in' the printed specification rcquiring'correction as follows: Page 2, line 103, for the, words a. symmetry read an asymmetry; and

that the said Letters Patent should be read with this, correction therein that the same may conform to the record of the case in the Patent Oflice.

. .Signed and sealed this 26th day .of December, A. D., 1911.

o. c. BILLINGS,

, ISEALZ] Acting Commissioner of Patents. 

